GlaxoSmithKline’s contract manufacturer has experienced unspecified manufacturing issues that are expected to set back supplies of its restless leg treatment Horizant until June.

“Manufacturing delays of Horizant have resulted in an insufficient amount of the product in the supply chain in the near term,” GSK spokesman Juan Carlos Molina told Outsourcing-Pharma.com.

“As a result, certain patients who have been prescribed or are refilling prescriptions for Horizant may not be able to have such prescriptions filled in the near term. Such situations are often referred to as ‘spot outages.’ … GSK is working to rectify the situation as quickly as possible,” Molina added.

The shortage comes as GSK shifts further development, manufacturing and commercialization of Horizant to co-developer XenoPort on May 1. GSK has also agreed to supply the drug for XenoPort until Oct. 30. And perhaps in an effort to assuage partners that it’s doing its due diligence with its suppliers, GSK recently decided to increase its audits
of them as part of a “risk-mapping” initiative.

The FDA updated its list of drug shortages
on Wednesday to include Horizant. XenoPort said in a statement that it does not anticipate “full commercial introduction” of Horizant to commence until a sufficient supply of it is available.

CEO of XenoPort Ronald W. Barrett, said: "We are obviously disappointed by this news, particularly since we have received inquiries from patients who have been unable to get theirHorizantprescriptions filled.”

“We are working with GSK and its contract manufacturer to expedite the next Horizant manufacturing campaign, and we are also advancing our plans to work directly with the contract manufacturer as soon as possible,” Barrett continued.

In November, GSK and XenoPort terminated their collaborative agreement on the drug. The terms of this decision required GSK to provide XenoPort with inventory of Horizant that is not required for use by GSK in the manufacture of the drug. In exchange for this inventory, XenoPort agreed to pay $1M for six years beginning in 2016.

But XenoPort still has the option until mid-May to require GSK to purchase up to an additional $20M of its common stock at a 12.5% premium to the average of the closing prices of XenoPort's common stock for the 10 trading days prior to the day XenoPort notifies GSK of its decision to exercise this option.

Horizant is also approved and marketed in Japan, where it’s known as Regnite. Astellas Pharma holds all development and commercialization rights for Regnite inJapan and five other Asian countries, according to GSK. Astellas did not respond to a request for comment on whether it was experiencing a shortage as well.

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